The present invention relates to a safety switch which is attached to a wall surface around a protection door to industrial machines, for example, and which is designed to cut off power supply to the industrial machines when the protective door is opened.
Conventionally, the safety switch is installed at the protective door to the industrial machines or the like in order to avoid a trouble wherein a worker is injured by being accidentally caught in a working machine. The safety switch is designed to disable the machines when the protective door is not completely closed. One example of such a safety switch is disclosed in, for example, Patent Document 1.
The safety switch is electrically connected with the industrial machines via a cable 610. As shown in FIG. 12A, the safety switch comprises a switch body 100 and an actuator 300.
The switch body 100 comprises an operation portion 500 and a switch portion 700 and is fixedly attached to a wall surface (not shown) around the protective door to the industrial machines. The actuator 300 is secured to the protective door and is located at place opposite either one of insertion holes (entrance holes) 900a, 900b formed at an upper side or a lateral side of the operation portion 500 such that the actuator may enter into the insertion hole 900a, 900b while the protective door is closed. As shown in FIG. 12A, the actuator 300 comprises: a base 300a; a pair of pressing pieces 300b projecting from the base 300a; and a connecting piece 300c interconnecting these pressing pieces 300b. In this case, the pressing pieces 300b is configured to have a small width and a great thickness and to define a U-shaped section through the connecting piece 300c. 
The switch portion 700 is constituted such that a switching device and an operating rod 211 are disposed in a case member 330. A lower outside surface SO of the case member is formed with a cable lead-out port 330a. The cable 610 connected with the switching device and the like in the switch portion 700 is led out through the lead-out port so as to be connected with the industrial machines and the like. As shown in FIG. 12A, an outside surface of the case member 330 is formed with a pair of receiving holes 330b through which bolts are inserted to mount the switch body 100 to the wall surface around the protective door to the industrial machines. A constitution is made such that a case member 110 of the operation portion 500 is removably attached to the case member 330 by means of an engaging claw or the like.
The operation portion 500 is constituted such that a driving cam 151 rotatably supported by a rotary shaft 131 axially supported by an inside surface of the case member 110 is disposed in the case member 110. An upper part of an outer periphery of the driving cam 151 is formed with two recesses (engaging portions) 151a1, 151a2 in which the connecting piece 300c of the actuator 300 is fittingly inserted. The recesses are formed at such positions as to be exposed to outside through the aforesaid insertion holes 900a, 900b. A lower part of the outer periphery of the driving cam 151 is formed with a cam curve portion 151c including a greater diameter portion and a smaller diameter portion. The operating rod 211 is constituted such that a tip portion thereof is free to project from or retract into the switch portion 700. The operating rod 211 is biased by a coil spring or the like in a direction of an UP-pointing arrow, so that the semi-spherical tip of the operating rod projects into the operation portion 500 to make sliding contact with the cam curve portion 151c of the driving cam 151.
The actuator 300 is advanced into the insertion hole 900a or 900b of the operation portion 500 by closing the protective door, so that the connecting piece 300c of the actuator 300 is fittingly inserted into the recess 151a1 or 151a2 of the driving cam 151. As the actuator 300 in fittingly inserted relation with the driving cam is advanced further into the operation portion 500, the driving cam 151 is rotated in a direction of an arrow α in FIG. 12B. Thus, the operating rod 211 slides on the driving cam 151 from the greater diameter portion to the smaller diameter portion of the cam curve portion 151c, so that the operating rod 211 moves in the direction of the UP-pointing arrow to shift the switching device of the switch portion 700 between on and off states.
Another example of the conventional safety switch is shown in FIG. 13A. As shown in the figure, the safety switch has a constitution wherein actuator insertion holes 900c, 900d are collectively formed at one corner portion of the case member 110 constituting the operation portion 500. In this case, a driving cam 152 rotatably supported by a rotary shaft 132 pivotally mounted to the inside surface of the case member 110 is disposed in the operation portion 500 of the switch body 101, as shown in FIG. 13B. An upper part of an outer periphery of the driving cam 152 is formed with a recess (engaging portion) 152a in which the connecting piece 300c of the actuator 300 is fittingly inserted. The recess is formed at such a position as to be exposed to outside through the aforesaid insertion holes 900c, 900d. Cam curve portions 152c1, 152c2, each including greater and smaller diameter portions, are formed at a lower part of the outer periphery of the driving cam 152. Similarly to the above safety switch, a semi-spherical tip of an operating rod 212 makes sliding contact with the cam curve portions 152c1, 152c2 of the driving cam 152. It is noted here that the cam curve portions 152c1, 152c2 comprise the cam curve portions 151c shown in FIG. 12B arranged in transversely symmetrical relation. As compared with the example of FIG. 12B, the example of FIG. 13B includes only one recess but two cam curve portions.
In a case where the actuator 300 enters into the operation portion 500 through the insertion hole 900c of the operation portion 500, the driving cam 152 is rotated in the direction of the arrow α in FIG. 13B. In a case where the actuator 300 enters into the operation portion 500 through the insertion hole 900d, the driving cam 152 is rotated in a direction of an arrow β in FIG. 13B. In this manner, the driving cam 152 is rotated in the direction of arrow α or arrow β, whereby the operating rod 212 slides on the driving cam 152 from the greater diameter portion to the smaller diameter portion of the cam curve portion 152c1, 152c2, so that the operating rod 212 moves in the direction of the UP-pointing arrow to shift the switching device of the switch portion 700 between the on and off states.
Patent Document 1: Japanese Unexamined Patent Publication No. 2002-140962 (Paragraphs [0040] to [0044], FIG. 1)